1. Field of the Invention
The present invention relates to a method of recording/reproducing optical disks having audio and video signals recorded thereon, and to such optical disks, and further to an apparatus for and a method of reproducing audio and video signals from such optical disks.
2. Description of the Related Art
Recently, disk reproducing apparatuses have been developed for reproducing audio and picture images recorded on an optical disk. Such disks are being utilized for storing movies, software and karaoke, for example. Further, reproduction apparatuses for reproducing speech data and picture data digital-recorded on an optical disk are also known, and are commercially available as karaoke systems, for example. The above optical disk is the same size as a CD (compact disk) so that the entire reproducing apparatus can be miniaturized.
FIG. 9 is a view illustrating a recording format for such an optical disk.
As illustrated in FIG. 9, the recording format comprises a read-in area 1, an information area 2, a data area 3, and a read-out area 4. A track (program) 1 corresponds to the information area 2. Tracks 2 up to 99 are disposed in the data area 3 and contain compressed video data and compressed audio data. Each track (program) in the data area 3 comprises, physically, an array of video data V and audio data A separated in sectors as illustrated in FIG. 10, wherein there are arranged about six successive video sectors V and one audio sector A, such that a video signal and a sound signal are synchronized.
A control table indicative of a reproduction procedure of a program stored in the data area 3 is recorded in the information area 2. In the case of a movie for example, since one movie comprises a series of programs, a control table indicative of a reproduction procedure among these programs is essential. A disk reproduction apparatus previously stores the control table in a memory upon starting the reproduction of a disk, and continuously reproduces the programs in conformity with the procedure recorded in the control table. A greater memory capacity is therefore required for the disk reproduction apparatus having a memory that is capable of storing all of the contents in the control table.
Recently, compression encoding of audio data and video data has been done using the MPEG (Moving Picture Image Coding Expert Group) system of the International Standard Specification, which comprises data in a variable length. It is theoretically possible to control with the control table such information of a GOP (Group of Picture) being a coding unit of an MPEG video signal as a sector and a position (bit) in the sector where the GOP exists, in order to improve a random access property. Construction of such a control table, however, complicates processing on the system side, and in addition, requires a greater memory capacity. Accordingly, such control is limited in practice to that on the program unit basis.
Accordingly, a conventional reproduction apparatus is required to have a greater memory capacity for storing the contents in a control table recorded on a recording medium. Further, data control on a control table is limited to a case where it is executed by a program basis and hence fails to have a satisfactory random access property.